The objective of this project is the investigation of CdBP (metallothionein, Mt) and the elucidation of its properties, particularly as those involve Cd-toxicity, by means of the RIA developed in my laboratory. It is now understood that Mt (or its precursor, thionein (Th)) is ubiquitous, is present with minor variations in vertebrates and invertebrates, and not only binds Cd but Cu, Hg, and other metals of toxicologic interest, as well as functioning in a fundamental physiological manner in Zn metabolism. The principal objectives involve the continued clarification of Th-Mt-metal relationships of both general and specifically toxicologic interest. The RIA will be used for Mt determination in body fluids and tissues in conjuction with established techniques, for examples, AAS, chromatography, etc., to determine metal concentrations in collaborative experiments involving Cd-toxicity in Cd-exposed workers, animals (primarily rats) treated with Cd, Zn, Cu, Hg, and possibly also Pb, Au, Bi, and possibly some invertebrates (mussels) exposed environmentally to some of the above metals. Additionally, a study in hybridomas will be initiated to attempt to refine the RIA so as to permit distinguishing between Mt and its precrusor. Should this latter effort be successful, then investigators in the properties of Mt, including toxicologists, will have the complete spectrum of research tools needed for the definitive resolution of the manner of functioning of the Th-Mt-metal network.